Download IONIC AND COVALENT COMPOUNDS A. Why do Atoms Form

IONIC AND COVALENT COMPOUNDS
A. Why do Atoms Form Bonds?
1. Stability
a) chemical bond =
** these are broken and reformed to provide for stability
within compounds
b) octet rule =
** atoms form bonds in order to take on the electron
configuration of a _____________ (they have stable octets!)
** results in “stability”
2. Potential Energy and Stability
a) energy = the ability to do work
b) bond energy =
** measured in KiloJoules/mole
** it takes energy to overcome the forces of attraction between
atoms and separate them
** __________ bonds are _________ and require large amounts of
energy to break them.....said to be in a ____ energy state.....
usually __________________
** _________ bonds are ___________ and require little energy to
break them.....said to be in a _______ energy state.....usually
_________________
c) electron transfers can occur in order to achieve stability within
compounds
** ions are formed [ex. Na → Na+ when an electron is
transferred to Cl → Cl- resulting in the formation of
a _____________
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3. Cation and Anion Formation
a) ionic bond =
.....occurs when electrons are transferred from ___________ to
___________ forming ______ (+ charged) and anions (- charged)
b) ionic compound =
....the compound is __________________________
c) salt = an ionic compound containing cations other than H+ and
anions other than OH- and O2d) properties of salts:
(1) made of _______________
(2) do NOT ___________________ in the ________ phase but DO
conduct electricity when ____________________________....
called ______________________
(3) form ______________ = repeating pattern to ion arrangement
** called a ______________________
** one unit of crystal = ___________________
(4) have high melting and boiling points [Table 8-2 p.218]
(5) hard and brittle
** due to layering that occurs within the crystal
** if the ions are moved within the layer however, like
ions align and the crystal ______________!
B. How Do You Name Salts? [naming chemical substances =______________]
1. Naming Ions (based on the chemical symbols within the periodic table)
a) monatomic ions = cation or anion formed from a single atom
** cations = use the element’s name (followed by ion)
ex. Na+ = sodium ion Mg2+ = magnesium ion
** anions = drop the suffix of the element’s name and add -ide
ex. Cl- = chloride ion S2- = sulfide ion
** oxidation number =
[Table 8-5 p.222]
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b) polyatomic ions =
** usually, atoms making up these ions are bound very tightly
and do not ordinarily break apart during chemical
reactions.....they ________________ (they behave as though
they were monatomic ions)
** many are ________________ = contain oxygen
ex. NO3- = nitrate NO2- = nitrite OH- = hydroxide
NH4+ = ammonium SO42- = sulfate
[Table 8-6 p.224 & Oxidation Sheet]
c) multiple-charge ions =
[Overhead]
ex. Cu+ Cu2+
Fe2+ Fe3+
** two systems can be used to identify which ion is used
(1) Stock system =
ex. Cu+ = Copper (I) Cu2+ = Copper (II)
(2) Traditional system =
** lower charge uses -ous Cu+ = cuprous
** higher charge uses -ic Cu2+ = cupric
2. Chemical Formulas
a) definition =
** even though there are only ~113 known elements....there are
over 10 million known compounds!!
b) two purposes:
(1) to indicate the composition of a compound.....tells what
elements make up the compound.....using symbols
** ____________________________
(2) to indicate the number of atoms of each element in one
molecule/formula unit.....uses “subscripts”
** ____________________________
** the subscript applies to the symbol that precedes it in
the formula
** no subscript....it is understood that there is one atom
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c) formula unit =
** CaO H2O
** a universal term....can be used to recognize ionic and
molecular compounds
** ex. 2CaO 2 formula units of calcium oxide
d) molecule =
(1) monatomic molecule = __________________________
** He Ne Ar (the noble gases)
(2) diatomic molecules = _____________________________
** Br I N Cl H O F
(Br2 N2 H2)
(3) binary/ternary molecules = ___________________________
_______________________
** CO2 H2O C6H12O6
e) kinds of formulas:
(1) steps used to determine the formula of a new substance.....
(*) Qualitative analysis = tells what elements are in the
compound.....may involve chemical tests (indicators
and test papers)
** exs. Hydrogen....burning splint barks
Oxygen....glowing splint reignites
Hydrochloric acid....turns blue litmus red
(*) Quantitative analysis = tells how much of each
element is present
** knowing the masses of the elements enables the
chemist to calculate the relative number of
atoms of each element
(2) Empirical formulas =
** used to help identify molecular formulas
** exs. H2O2  HO
C4H8  CH2
C6H6  CH
MgCl2  MgCl2
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(3) Molecular formulas = gives type and actual number of atoms
in a chemical compound
** exs. H2O  molecular & empirical
H2O2  molecular
HO  empirical
C6H12O6  molecular CH2O  empirical
** note: even though some compounds may have the same
empirical formula, their properties are entirely
different [Overhead]
(4) Structural formulas =
** it is the unique structure of each substance that gives it
it’s unique set of properties!
** ex. methane
H
[Overhead]
H- C -H
H
3. Types of Compounds
a) Review.....
(1) metals -- left/middle of P.T.; give up electrons to form
cations; become more reactive down a group (Fe, Cu, Li)
(2) nonmetals -- right of P.T.; accept electrons to form anions;
become less reactive down a group (O, P, S)
(3) semimetals -- aka: metalloids; separates the metals & the
nonmetals; have properties of both (B, Si, Ge)
b) two major classes of compounds:
(1) _________________ = usually formed when a metal transfers
an electron to a nonmetal (aka: electrovalent bond)
** exs. NaF MgCl2
(2) __________________ = usually formed when nonmetals
share electrons
** exs. CO2 H2O
4. Writing the Formulas for Ionic Compounds
a) ionic formulas are always represented by empirical formulas!!
b) Binary ionic compounds =
** note.... the total _____________ charge must equal the total
______________ charge
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** Rules:
(1) Write the symbols for the two ions....cation is written
first (name of the element) followed by the anion
(element name ending in -ide)
** use the oxidation sheet to help determine the
charges on the ions
** some ion charges can be determined by their
positions in the P.T. (ex. Group 1 = +1)
(2) Find the least common multiple of the ions’ charges....
provides for a _________________....sometimes called
the criss-cross method....place a _____________ beside
symbol of the ion needing more than one
** examples: NaCl
MgBr2 K2O Ba3N2
c) Ternary ionic compounds =
** involves _______________________
** Rules:
(1) Write the symbols for the two ions....cation 1st followed
by the anion
(2) Find the least common multiple of the ions’ charges....
if more than one polyatomic ion is needed to balance
the formula, place it in parentheses and put the
subscript outside
** examples: NH4F Na2SO4 Ca(OH)2 (NH4)3PO4
5. Naming Ionic Compounds
a) general rule of thumb = the name of the cation is usually the
name of the metal....the name of the anion is the name of the
nonmetal with the suffix -ide (for binary formulas)
** for ternary formulas.....use the name of the polyatomic ion
** examples:
Binary: NaF sodium fluoride
Ternary: NaNO3 sodium nitrate
Combo: NH4I ammonium iodide
b) two naming systems can be used (for multiple-ion elements):
(1) Traditional system.....uses suffixes (of Latin roots)
** -ous (lower charge) -ic (higher charge)
ex. CuBr cuprous bromide
CuBr2 cupric bromide
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(2) Stock system.....uses Roman numerals to identify the charge
** ex. CuBr copper (I) bromide
CuBr2 copper (II) bromide
** [Figure 8-8 p.227]
C. Formulas of Molecular Compounds
1. Molecular compound =
a) there are NO ions.....electrons are _______________ rather than
transferred
** octet rule = atoms lose, gain, or share electrons to achieve
a stable octet of electrons
** sometimes the _________________________________________
** there is no simple method for predicting and writing formulas
for molecular compounds.....many molecular compounds
have the same elements in them...just in different amounts
or having different structures
b) ____________________ = the apparent charge assigned to an atom
based on the assumption of complete transfer of electrons
** produced by an unequal sharing of electrons due to
electronegativity differences (atoms having the greater
attraction for the electrons is assigned an apparent
negative charge while the atoms having a smaller attraction
is assigned an apparent positive charge)
c) with oxygen.....
** Oxygen is always assigned an apparent charge of 2** helps determine the apparent charge on the other atoms it is
combined with
2. Naming molecular compounds
a) binary formulas
** composed of two nonmetals
** atom with positive oxidation # written 1st ....atom with
negative oxidation # written 2nd
b) systems used:
(1) traditional system uses prefixes [Overhead]
** mon(o)- di- tri- tetra- penta- hexa- heptaocta- nona- deca-
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** tells how many atoms of each element are in the
molecule
** used with both elements (one exception: if only ONE
atom of the 1st element..... mono is NOT used)
** the suffix of the 2nd element ends in Bide
** exs. carbon monoxide CO
dinitrogen trioxide N2O3
(2) stock system uses Roman numerals to show the apparent
charge on the atom with the positive oxidation #
** exs. carbon (II) oxide CO
nitrogen (VI) oxide N2O3
3. Organic compounds = compounds containing carbon
** READ 696-701 and 708-709
a) Hydrocarbons =
** simplest group are the _____________ = long chains of carbon
atoms linked to each other by single covalent bonds
** - C - C - C - C - C ** [Overhead]
** hydrocarbon stems (prefixes) are used to indicate the
___________________________________________
[stems: meth- (1) eth- (2) prop- (3) but- (4)
pent- (5) hex- (6) hept- (7) oct- (8) non- (9)
dec- (10) ]
** the suffix -ane is used with the stem to name the compound
** exs. CH4 methane
C4H10 butane
b) functional groups = group of atoms that determines an organic
molecule’s chemical properties [Overhead]
** exs. alcohols (rubbing), ethers (starting fluid),
aldehydes (formaldehyde), ketones (acetone),
organic acids (vinegar), amines (amino acids)
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D. Naming Acids
1. Acid =
2. Binary acids = __________________________
a) usually made by bubbling the gas through water
b) when named....hydrogen is placed 1st in the formula followed by
the nonmetal
** the prefix hydro + the name of the nonmetal + the suffix
-ic ending with acid
** exs. HF hydrofluoric acid
HBr hydrobromic acid
HCl hydrochloric acid H2S H2Te HI
3. Ternary acids = hydrogen + polyatomic anion
a) made by dissolving the dry solid in water
b) produces the cation H+ and polyatomic anions (usually oxyanions)...
thus resulting in ____________________
c) named by adding a suffix to the polyatomic ion
** -ate ions end in -ic (+ acid)
ex. H2SO4 sulfuric acid HNO3 nitric acid
** -ite ions end in -ous (+ acid)
ex. H2SO3 sulfurous acid HNO2 nitrous acid
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